Revision of the structure of strychnochromine

✍ Scribed by J. Quetin-Leclercq; L. Angenot; L. Dupont; O. Dideberg; R. Warin; C. Delaude; C. Coune

• Publisher: Elsevier Science
• Year: 1991
• Tongue: French
• Weight: 253 KB
• Volume: 32
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)92152-x

✦ Synopsis

The structure of strychnochrondne, an unusual alkaloid isolatedfrom the root bark of Shychnos gossweileri. has been revised. Strychnochrondne 2 possesses a new pentacyclic skeleton with a tetrahydroquinoline rather than indole or indoline moiety. Chemical investigations of the constituents of the root bark of Strychnos gossweileri Exe11 have resulted in the isolation of a number of alkaloids among which is the new and peculiar strychnochrominel-5. From spectroscopic data ( UV, IR, MS, one-dimensional 1~ and 13C NMR spectra ), structure 1, based on an indoline moiety, was proposed for this alkaloid. Unfortunately, the lack of material and of reference compounds did not allow us to confirm this hypothetical structure and determine its stereochemistry 6. Recently, we had the opportunity to analyse a new sample of the root bark of S. gossweileri collected in the same area. Beside known alkaloids, we isolated a new anhydronium base7 and further amounts of strychnochromine. In order to confirm its unusual structure and determine its stereochemistry, extensive 2D NMR experiments were carried out ( COSY, X-H Corr, NOESY, COLOC ). The COSY and X-H Corr experiments mostly confined the previous observations but the COLOC maps (J = 5, 7, 8, 10 or 15 Hz) did not fit the proposed structure. In particular, the connectivities observed between C-3 and H-3 and the neighbouring H and C cannot be explained by structure 1. Furthermore, it was not possible to find a structure based on an indoline skeleton that would agree with all the data.